Gemstone profile and identification guide
Opal
Opal is a Multicolour hydrated silicate prized for its distinctive beauty, historic appeal, and use in fine jewellery and collector pieces.
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Overview
Opal is a Multicolour hydrated silicate prized for its distinctive beauty, historic appeal, and use in fine jewellery and collector pieces.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Opal
Scientific classification: Hydrated Silicate
Hardness: 5.5 Mohs
Transparency: translucent
Lustre: pearlescent
Crystal system: Amorphous
Primary colour: Multicolour
Secondary colour: Not specified
Colour family: Special Optical Effects
Physical Properties
Hardness category: soft
Hardness value: 5.5 Mohs
Chemical composition: Hydrated silicon dioxide (SiO2?nH2O)
Crystal system: Amorphous
Common locations: Australia, Ethiopia, Mexico, Brazil
Learn more: Gem-A gemstone education resources.
Colour Variations
Opal is classified within the special optical effects palette. Primary colour: multicolour. Optical effects: Opalescence, Play of Colour, Iridescence.
Optical effects: Opalescence, Play of Colour, Iridescence
Formation
Forms from silica-rich solutions that seep into cracks and cavities, depositing microscopic spheres of silica over time.
Origin
Australia, Ethiopia, Mexico, Brazil
Uses
Best for: Jewellery, displays, and design accents.
Ideal uses: Versatile collections and polished showcases.
Care
Protect from drying out and avoid sudden temperature shifts. Clean with a damp cloth and mild soap.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Related gemstones by colour
Related gemstones by hardness
Gemstones from the same mineral family
Commonly confused gemstones
Opal FAQ
How can I identify Opal?
Compare hardness (5.5 Mohs), crystal system (Amorphous), colour profile, and lustre (pearlescent) with your sample. Then cross-check related gemstones listed above.
What colour range does Opal appear in?
Opal is classified within the special optical effects palette. Primary colour: multicolour. Optical effects: Opalescence, Play of Colour, Iridescence.
Where is Opal commonly used?
Versatile collections and polished showcases.. For maintenance, follow the care guidance in this profile.
Scientific References
Reference data from GIA and Mindat mineral records.